The present invention relates to an overturning device designed to operate in machines for wrapping groups of essentially soft commodities, typically rolls of kitchen paper, toilet tissue and the like, of which the longitudinal dimension parallel to the wrapping axis remains substantially stable whilst the transverse dimension, disposed perpendicular to and similar in proportion to the longitudinal, is liable to variation when subjected even to a light application of pressure; the single roll of paper is therefore a deformable commodity insofar as it can be compressed in the radial direction, though not in the axial.
Conventionally, commodities of the type in question (rolls of absorbent kitchen paper, toilet tissue) are wrapped by machines, as disclosed in Italian Patent 1 169 152, for example, comprising a feed station through which the commodities are conveyed in single file, advancing horizontally and disposed with the wrapping axis parallel to the conveying surface, and, associated with the feed station, an overturning device by which each emerging commodity is rotated through a right angle to a position in which the wrapping axis is disposed perpendicular to the conveying surface. The repositioned rolls are then arranged in groups to suit the particular packaging format and advanced toward a further station for wrapping, generally in plastic film. The patent overturning device referred to above takes the form (as do similar devices disclosed in U.S. Pat. No. 2,905,341, U.S. Pat. No. 4,564,104 and OS 2 145 599) of a power driven star wheel functioning synchronously with the other stations of the machine, and a guide positioned over one portion of the wheel. The star wheel and guide thus combine to create a channel describing an arc to a circle and extending from the pass line of the feed station to that of the wrapping station.
A solution of this type betrays certain drawbacks, relying as it does on extensive contact with the commodity and essentially mechanical in conception, namely: the overturning movement of the rolls has necessarily to bridge two distinct levels, with the result that the general architecture of the machine itself is rendered cumbersome by reason both of the offset between two operating levels, and of the need for mechanical linkages to connect the drive systems of the machine and the overturning device; what is more, the passage of the rolls through the star wheel is not without risk, especially in view of the change in direction that occurs, somewhat abruptly, on contact with the projections of the wheel. In this latter instance, the fact that the integrity of the product cannot be totally assured also prevents the constructor of the machine from stepping up the rated production tempo.
Accordingly, the object of the present invention is to overcome the drawbacks mentioned above through the provision of an overturning device for wrapping machines such as will be practical in embodiment, and capable of rotating the selected commodities with precision and sensitivity, at high speed, and on a pass line occupying a single plane.